The age of distributed manufacturing is upon us. This week, Amazon opened a section in its giant online store for 3D Printers & Supplies.

The section includes 3D printers, 3D printer filament, books, CAD software and related items. 3D printers include the featured Alfinia 3D Printer H-Series at $1,599 -- which Make Magazine said provided "the best overall experience" -- the MakerBot Replicator 2 Desktop 3D Printer for $2,479, and the Mbot Cube 3D Printer Dual Head at $1,299.

Amazon is not the only indication that the 3D printer revolution is here. Office-supply store Staples is selling Cube 3D printers, as well.

The RepRap Project

Commercially available 3D printers have recently moved from being expensive hobbyist devices to being pricey but accessible consumer devices, selling in the $1,000-$2,000 range. But there's also a movement to replicate 3D printers using -- what else? -- 3D printers, such as the RepRap project in the U.K.

Dr. Adrian Bowyer, a lecturer at the University of Bath in England, started the RepRap project to build a low-cost 3D printer that can print plastic objects and duplicate itself.

Bowyer completed the first RepRap printer in 2007, and he named it, appropriately enough, Darwin. He said he wanted to see if he could build a printer for a few hundred pounds, instead of the 30,000 pounds he paid at the time. The schematics were then made freely available online, and there are an estimated 20,000 users of RepRap printers now. Some of the models from the companies MakerBot and Bits from Bytes have used the RepRap specs as the basis for their commercial versions.

3D printers build objects by placing layer after layer of molten plastic on a base. While plastics are most commonly used, printer modifications have also enabled the use of such other materials as ceramics. Currently, a student of Bowyer's is working on creating a 3D printer than can build a computer motherboard, using both plastic and low-melting-point metal.

'Next Industrial Revolution'

The 3D printing community is growing, with sites such as MakerBot's Thingiverse offering printed objects for sale. Meanwhile, this week MakerBot opened a 50,000-square-foot factory in the Brooklyn borough of New York City to produce its printers. CEO Bre Pettis described 3D printing as the "beginning of the next industrial revolution."

But revolutions have consequences, and the ability to print almost any object has already raised concerns about a much wider proliferation of guns and other weapons. In May, for instance, the U.S. State Department ordered that blueprints for a 3D-printable handgun be removed from the Web.

The blueprints were posted online by a Texas-based organization called Defense Distributed. Since the 3D gun was made of plastic, it would be undetectable by airport and building weapons scanners.

Even before that federal order in May, MakerBot took the incentive to avoid connecting its product line with weapons makers. Following the shooting murders of elementary school children and teachers in Newtown, Conn., last December, the company began to remove gun designs from Thingiverse. Such designs had been banned, but a more active enforcement was implemented against posting designs or objects that "contributes to the creation of weapons."